Active hydrogen excretion and sodium absorption through isolated frog skin

Area of Science:

• Physiology
• Comparative Physiology
• Membrane Transport

Background:

• The skin of amphibians like Rana esculenta plays a vital role in ion and water balance.
• Understanding the mechanisms of active ion transport in amphibian skin is crucial for physiological studies.

Purpose of the Study:

• To investigate the in vitro mechanisms of sodium absorption and hydrogen excretion across Rana esculenta skin.
• To elucidate the relationship between sodium transport and proton excretion under various conditions.

Main Methods:

• Studied isolated Rana esculenta skin in open-circuit and short-circuit conditions.
• Utilized solutions of NaCl and Na2SO4 with varying concentrations.
• Measured net fluxes of ions (Na+, Cl-, SO42-) and proton excretion.
• Analyzed the correlation between sodium absorption and hydrogen excretion.

Main Results:

• Sodium absorption significantly exceeded chloride absorption in NaCl solutions.
• A strong correlation was observed between sodium absorption and hydrogen excretion (JnH+ = (-25 +/- 7) - (0.73 +/- 0.04) JnNa+).
• Hydrogen excretion demonstrated saturation kinetics, with maximum excretion at 4 meq sodium concentration.
• Under high Na2SO4 concentrations, sulfate absorption balanced the net sodium flux.
• Active hydrogen excretion was confirmed under short-circuit conditions.

Conclusions:

• Rana esculenta skin actively transports sodium and excretes hydrogen ions to maintain electrochemical neutrality.
• A model is proposed linking active proton excretion to the sodium transport mechanism.
• The findings contribute to understanding amphibian osmoregulation and ion transport physiology.